The focus of this research proposal will be to systematically investigate the Natural anti-tumor defense system of the liver including its regulation by biological and chemical response modifiers. We will isolate and fractionate nonparenchymal liver cells by various techniques (Metrizamide gradients, Centrifugal elutriation etc.) from inbred and genetically defined rats and mice. These isolated and purified populations of liver cells will be tested for their ability to lyse a panel of neoplastic and non-neoplastic cells in chromium release assays in vitro. In addition, we will use specific monoclonal or allogeneic antibodies to further characterize the effector cells in the liver responsible for cytotoxicity. Experiments will also be carried out to analyze the mechanism of lysis by effector cells in the liver using various protease and lysosomal enzyme inhibitors and in vitro assays (plasminogen activator, cytotoxic factor). We will attempt to modulate the anti-tumor activity of the liver by administering BCG and Adriamycin. Additionally, liposomes will be used as a delivery vehicle to target chemotherapeutic drugs (Adriamycin) to the liver to study their effect on various functions of the isolated liver cells including natural anti-tumor activity. Our laboratory has identified a factor produced spontaneously by rat hepatocytes, that can suppress the lysis of tumor cells by nonparenchymal liver cells in vitro. The biochemical nature of this hepatocyte suppressor factor (HSF) will be identified. An immunoradiometric assay for HSF will be developed. The effects of HSF on a multitude of nonparenchymal liver functions will be explored (superoxide, hydrogen peroxide, interleukin-1, phagocytosis). The effects of an antibody to HSF on liver function will be evaluated in vitro and in vivo. In conclusion, we will attempt to analyze the ability of the liver to resist neoplasms. This will include identification of resident effector cells, determining their specificity of response, their endogenous regulatory mechanisms and finally the modulation of their activity with exogenous agents. These studies should lead to new approaches to control liver cancer which at present has a poor prognosis.